The present application relates to Group V and VI metal complexes and in particular to their use in supported form as catalysts for the polymerisation of olefins. The invention specifically relates to the use of polymer-supported catalysts.
Catalysts comprising transition metals have been widely used for polymerisation reactions. For example bis(cyclopentadienyl) metal complexes containing zirconium or titanium have long been recognised as an important class of catalyst systems for the Ziegler-Natta polymerisation of olefins, when used with suitable cocatalysts.
Such metallocenes are becoming more and more important as catalysts which may be used to produce polymers with selected and improved properties.
Another type of transition metal complex useful as catalysts is disclosed in EP 641804A.
This reference describes novel Group V and VI metal-imido complexes, in particular chromium-imido complexes, which show promise as alternative catalysts for the polymerisation of olefins to the more established metallocene or Ziegler type catalysts.
When used in the gas phase such complexes may be suitably supported on conventional supports such as inorganic oxides (silica, alumina), magnesium halides or polymers such as polyethylene may be used as supports.
More recently both metallocenes and their cocatalysts (alumoxanes) have been supported on substrates comprising cross-linked polymeric porous resins for example see WO 95/23816 and U.S. Pat. No. 5,362,824.